<!DOCTYPE html>
<html>
<head lang="en">
    <meta charset="UTF-8">
    <title></title>
</head>
<body>


<div id="header" >
  <h1>Welcome to Html</h1>
</div>

<div class="mainContent">

</div>

<div class="mainContent">

</div>

<div id="footer">

</div>

<script type="text/javascript" src="app.js"></script>
</body>
</html>